Abbreviation for LED Light Emitting Diode. It is a solid-state semiconductor device LED CHIP that directly converts electricity into light. The heart of the LED is a semiconductor wafer. One end of the wafer is attached to a holder, one end is the negative pole, and the other end is connected to the positive pole of the power supply, so that the entire wafer is encapsulated by epoxy resin. The semiconductor wafer consists of two parts, one part is a P-type semiconductor, in which the hole dominates, and the other end is an N-type semiconductor, which is mainly electrons here. But when the two semiconductors are connected, they form a PN junction. When a current is applied to the wafer through the wire, the electrons are pushed toward the P region. In the P region, electrons recombine with the holes, and then the energy is emitted in the form of photons. This is the principle of LED illumination. The wavelength of light, which is the color of light, is determined by the material that forms the PN junction.
What is a led chip:
Also known as the LED light-emitting chip, it is the core component of the LED LAMP, which is also referred to as the PN junction. Its main function is to convert electrical energy into light energy. The main material of the chip is monocrystalline silicon.
Classification of led chips: According to the use, it is divided into high-power LED chip and low-power LED chip;
Color: Mainly divided into three types: red, green, blue (raw materials for white light);
Shape: Generally divided into square pieces and round pieces;
Size: Small power chips are generally divided into 8mil, 9mil, 12mil, 14mil, etc.
How to judge the LED chip:
The price of led chip: In general, the price of the film below is higher than the price of the wafer. The high-power LED chip must be higher than the low-power LED chip. The imported price is higher than that of the domestic one. The imported source price is from Japan, the United States, Taiwan has been reduced in turn.
The quality of the led chip: The quality of the led chip is mainly measured from the two main standards of bare crystal brightness and attenuation. In the packaging process, the yield of the LED chip package is mainly calculated.
The LED chip we use:
Red light: 9mil regular square, (pure red) wavelength: 620-625nm, up and down 60°, left and right 120°, brightness up to 1000-1200mcd;
Green light: 12 mil regular square, (pure green) wavelength: 520-525nm, up and down 60 °, left and right 120 °, brightness up to 2000-3000mcd;
Performance: It has the characteristics of high brightness, strong antistatic ability, strong anti-attenuation ability and good consistency. It is the best choice for making led signs and led letters.
LED counting method:
LED chips are generally in size: small power chips are generally divided into 8mil, 9mil, 12mil, 14mil, etc., as thin as the hair, the previous manual counting is very hard, and the accuracy is extremely low, now Xiamen Haojing Technology has developed A set of software specifically for LED chip counting, the instrument integrates high-definition digital technology to identify the most difficult counting problems. The LED chip-specific counter device is made up of megapixel industry-specific CCD and megapixel lens hardware. The software that integrates high-definition image digital technology is mainly used to calculate the number of LED chips. The LED chip dedicated counter is capable of accurately and quickly counting LED chips through high-speed image acquisition and visual recognition processing, and is simple in operation and convenient to use.
The device is equipped with a new lighting configuration. Due to the uniformity of illumination and the application of megapixel CCD and lens, the image clarity of the LED chip is ensured, and high-tech counting software is used to ensure the accuracy of counting. . At the same time, the software will store the results of each count in the database, which is convenient for printing and retrospective comparison analysis.
Technical Parameters:
1. Imaging characteristics lens: 12mm, F1.8 high fidelity optical lens CCD specifications: 3 million pixels / 5 million pixels, true color image shooting: manual focus, professional level fine imaging LED chip image adjustment: manual adjustment of brightness; automatic adjustment of contrast ,saturation
2. Counting characteristics:
Quickly calculate the total number of LED chips, can be discounted according to the need, and display and output count results can be counted ≥ 5mil (or 0.127mm) opaque LED chip can count two-electrode transparent LED chip counting speed: 2000 ~ 8000 LED chips / The statistical speed of s, no need to scan, ie imaging, counting is easy to use: the real one-button operation, the mouse, the result is now. The software interface is beautiful and easy to operate.
Interpretation of important parameters of LED:
1. Forward working current If:
It refers to the forward current value when the light-emitting diode is normally illuminated. In actual use, the IF should be selected below 0.6·IFm as needed.
2. Forward working voltage VF:
The operating voltages given in the parameter table are obtained at a given forward current. It is generally measured at IF = 20 mA. The forward working voltage VF of the light-emitting diode is 1.4 to 3V. As the outside temperature rises, the VF will drop.
3.VI features:
The relationship between the voltage and current of the light-emitting diode is such that when the forward voltage is less than a certain value (called a threshold), the current is extremely small and does not emit light. When the voltage exceeds a certain value, the forward current rapidly increases with the voltage and illuminates.
4. Luminous intensity IV:
The luminous intensity of the light-emitting diode generally refers to the luminous intensity in the direction of the normal line (for the axis of the cylindrical light-emitting tube). If the radiation intensity in this direction is (1/683) W/sr, then the light can be 1 candela (symbol cd). Since the general LED has two small illuminances, the illuminance is usually a candle (candela, mcd) unit.
5. LED illumination angle:
-90°- +90°
6. Spectral half width Δλ:
It represents the spectral purity of the light-emitting tube.
7. Half value angle θ 1/2 and viewing angle:
θ 1/2 means an angle between the direction in which the luminous intensity value is half of the axial intensity value and the axial direction of the light emission (normal direction).
8. Full shape:
The angle converted from the solid angle of the LED illumination is also called the plane angle.
9. Perspective:
Refers to the maximum angle of LED illumination, depending on the viewing angle, the application is also different, also called the light intensity angle.
10. Half shape:
The angle between the normal 0° and the maximum luminous intensity value/2. Strictly speaking, it is the angle corresponding to the maximum luminous intensity value and the maximum luminous intensity value of /2. The LED packaging technology results in the maximum illumination angle not being the normal 0° intensity value, and the introduction of the deviation angle refers to the angle between the angle corresponding to the maximum illumination intensity and the normal 0°.
11. Maximum forward DC current IFm:
The maximum forward DC current allowed to be applied. Exceeding this value can damage the diode.
12. Maximum reverse voltage VRm:
The maximum reverse voltage allowed to be applied. Above this value, the light-emitting diode may be damaged by breakdown.
13. Working environment topm:
The ambient temperature range over which the LED can operate. Below or above this temperature range, the LED will not work properly and the efficiency will be greatly reduced.
14. Allow power consumption Pm:
The maximum value of the product of the forward DC voltage applied across the LED and the current flowing through it. Above this value, the LED is hot and damaged.
Editor: China Lighting Network Feng Yaoyuan
